INFLUENCE HALOGEN IN REACTION ARYLTELLUR TRYHALOHENIDE ELECTROPHILIC CYCLIZATION OF N-ALKENYL OF 2-TIOXOBENZO (THIENO)PYRIMIDIN-4-ONES

Abstract

It is known from the literature that electrophilic heterocyclization of unsaturated substrates under the action of aryltellurium trichlorides is widely used to obtain tellurium-containing polycondensed heterocyclic systems, whereas the use of p -alkoxyphenyltellurium tribromides in such reactions is almost not described. p -Ethoxyphenyltelluriumtribromide was used for study the influence of a halogen in the electrophilic aryltelluronium reagent on products' yields and on the direction of the electrophilic intramolecular cyclization of N-alkenyl-2-thioxobenzo(thieno)pyrimidine-4-ones. It was not possible to obtain this electrophile with the reaction of tellurium tetrabromide with benzene containing electron donating group, so it was synthesized by bromination of the corresponding ditelluride in chloroform medium. The interaction between tellurium-containing electrophile and N-alkenyl-2-thioxobenzo(thieno)pyrimidine-4-ones was carried out in glacial acetic acid at room temperature. It has been established that during aryltellurobromination of 3-allyl-quinazoline-2-thione and N-alkenyl thioxo-thieno-pyrimidinones, the annelation of the thiazoline ring takes place, with the formation of a linear condensed system with an exocyclic aryltellurium fragment – hydrobromides of 3-[dibromo(4-ethoxyphenyl)telluromethyl]-2,3-dihydro-5 H -[1,3]thiazolo[2,3-b]quinazolin-5-one, 2-(dibromo(4-ethoxyphenyl)-telluromethyl)-2,3,6,7,8,9-hexahydro-5 H -benzo[4,5]thieno[2,3-d][1,3]thiazolo[3,2-a]pyrimidin-5-one and 2-methyl-2-(dibromo(4-ethoxyphenyl)-2,3,6,7,8,9-hexahydro-5 H -benzo[4,5]thieno[2,3-d][1,3]thiazolo[3,2-a]pyrimidine-5-one. The structure of the products of bromotelluro-cyclization is similar to the structure of products of aryltellurochlorination of the corresponding heterocycles. However, the yields of salts with the exocyclic bromoaryltellurium fragment are smaller compared to chloro- analogs. Lower yields of hydrobromides are associated with lower stability of intermediate bromotelluronium cation compared with chlorotelluronium, which is confirmed by theoretical calculations of Gibbs free energy of interaction of aryldihalidetellanium cation with an unsaturated substrate. Computations were performed using DFT level of theory in PRIRODA 17 program with using of GGA PBE functional and 3ζ basis set. The effect of solvent medium (acetic acid) was taken into account using the COSMO model with PM7 Hamiltonian in MOPAC2016 program. The composition and structure of all obtained compounds are proved by elemental analysis and NMR spectra.